1. Field of the Invention
The present invention relates to a 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent, a method for producing the photosensitive agent, and a photoresist composition. More particularly, the present invention relates to a 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent which has high solubility in solvent and is a useful photosensitive agent for a photoresist used for producing semiconductor integrated circuits, liquid crystal displays, etc., a method for producing the photosensitive agent, and photoresist composition containing the photosensitive agent.
2. Description of the Related Art
photosensitive agents containing a 1,2-naphthoquinone-2-diazidesulfonate ester are generally used in positive-type photoresists as a photosensitive component, in combination with an alkali-soluble binder resin such as a novolak resin. The positive-type photoresists, having high resolution, are used for producing semiconductor integrated circuits, liquid crystal displays, EL displays, etc.
Generally, the 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent serving as a photosensitive component of such positive-type photoresists is produced by reacting a polyphenolic compound and 1,2-naphthoquinone-2-diazidesulfonyl chloride in the presence of a neutralizing agent. Polyphenolic compounds known to be used in the above reaction include polyhydroxybenzophenones (W. S. Deforest, xe2x80x9cPhotoresist,xe2x80x9d McGraw-Hill Book Company, 1975, p. 48-55 and Japanese Patent Application Laid-Open (kokai) No. 62-153950); polyhydroxytriphenylmethanes (Japanese Patent Application Laid-Open (kokai) No. 1-189644); and polyphenolic compounds, each being formed by linking 3, 4, or 5 phenol molecules with methylene (WO90/07538 and Japanese Patent Application Laid-Open (kokai) Nos. 6-167805 and 7-120917). 1,2-Naphthoquinone-2-diazidesulfonate esters can be produced at low cost from polyhydroxybenzophenone, inter alia, trihydroxybenzophenone and tetrahydroxybenzophenone. Therefore, 1,2-naphthoquinone-2-diazidesulfonate esters are employed as a photoseisitive component of a photoresist for producing semiconductor integrated circuits and liquid crystal display.
Polyhydroxybenzophenones show a high absorption at i-line (365 nm), and a photoresist containing a polyhydroxybenzophenone provides a poor pattern form through exposure to i-line. Thus, such a photoresist is employed for exposure to g-line (436 nm). Photoresists employed for exposure to i-line generally contain polyhydroxytriphenylmethanes or polyphenolic compounds formed by linking 3, 4, or 5 phenol molecules with methylene. However, production of such polyphenolic compounds involves cumbersome steps, and the thus-produced polyphenolic compound has poor solubility in a resist solvent. Thus, a photoresist composition containing the polyphenolic compound raises problems; i.e., the composition may fail to attain sufficient dissolution of the photosensitive agent and possibly form unfavorable precipitates with the elapse of time.
Japanese Patent Application Laid-Open (kokai) No. 3-279957 discloses a 1,2-naphthoquinone-2-diazidesulfonate ester produced from a polyhydroxy compound, which is a cyclic polyphenolic compound that does not show an absorption at i-line and can be produced through an easy process. However, such a 1,2-naphthoquinone-2-diazidesulfonate ester produced from a cyclic polyhydroxy compound has also poor solubility in a resist solvent, and a photoresist composition containing the ester raises problems; i.e., the composition may fail to attain sufficient dissolution of the photosensitive agent and possibly form unfavorable precipitates with the elapse of time.
As described above, a variety of polyphenolic compounds and 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agents derived from the polyphenolic compounds are disclosed. However, there has not been known a 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent having high solubility in a resist solvent, which ester is derived from a polyhydric phenol that does not show an absorption at i-line and can be produced through a simple process.
In order to solve the aforementioned problems, the present inventors have carried out extensive studies on 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agents produced from a cyclic polyhydroxy compound disclosed in Japanese Patent Application Laid-Open (kokai) No. 3-279957, which does not show an absorption at i-line and is easily produced; and have found that a specific 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent obtained from a polyhydric phenol; i.e., a cyclic polyhydroxy compound produced through condensation of resorcinol and at least one aldehyde selected from C3-C10 aldehydes and containing higher-molecular-weight components in an amount below a certain level, has high solubility in a medium such as resist solvent, and that a photoresist composition containing the photosensitive agent exhibits satisfactory sensitivity and excellent storage stability and serves as a highly useful composition. The present invention has been accomplished on the basis of these findings.
Thus, an object of the present invention is to provide a 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent which is useful as a photosensitive agent employed in a photoresist for producing semiconductor integrated circuits, liquid crystal displays, EL displays, etc. Another object of the invention is to provide a method for producing the photosensitive agent. Still another object of the invention is to provide a photoresist composition containing the photosensitive agent.
Accordingly, in a first aspect of the present invention, there is provided a 1,2-Naphthoquinone-2-diazidesulfonate ester photosensitive agent which is produced by reacting a polyhydric phenol(polyphenol) with 1,2-naphthoquinone-2-diazidesulfonyl chloride in the presence of a neutralizing agent, wherein the polyhydric phenol is obtained by a condensation reaction between resorcinol and at least one aldehyde selected from C3-C10 aldehydes, and contains, as a predominant component, a compound represented by formula (I) and components exhibiting a retention time as measured by using GPC shorter than that of the compound represented by formula (I) in an amount of 10% or less: 
wherein each of R1, R2, R3, and R4 represents a C2-C9 alkyl group.
The polyhydric phenol containing the compound represented by formula (I) as a predominant component may contain, in an amount of 5% or less, components exhibiting a retention time as measured by using GPC shorter than that of the compound represented by formula (I).
Each of R1, R2, R3, and R4 in formula (I) may be a C4-C6 alkyl group.
The polyhydric phenol containing the compound represented by formula (I) as a predominant component may be reacted with 1,2-naphthoquinone-2-diazidesulfonyl chloride in an amount of at least 3 mol based on 1 mol of the polyhydric phenol.
The 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent may be incorporated into a photoresist for exposure to i-line.
In a second aspect of the present invention, there is provided a photoresist composition comprising any of the aforementioned 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent and an alkali-soluble resin.
The photoresist composition may be employed for exposure to i-line.
In a third aspect of the present invention, there is provided a method for producing a 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent comprising the steps of: obtaining a polyhydric phenol by a condensation reaction between resorcinol and at least one aldehyde selected from C3-C10 aldehydes, which the polyhydric phenol contains, as a predominant component, the compound represented by formula (I), and components exhibiting a retention time as measured by using GPC shorter than that of the compound represented by formula (I) in an amount of 10% or less: 
wherein each of R1, R2, R3, and R4 represents a C2-C9 alkyl group; and reacting the polyhydric phenol with 1,2-naphthoquinone-2-diazidesulfonyl chloride in the presence of a neutralizing agent.
The 1,2-naphthoquinone-2-diazidesulfonate ester photosensitive agent according to the present invention, which is derived from a polyhydric phenol predominantly containing a cyclic compound represented by formula (I), exhibits high solubility in solvent and can be produced, through an easy process, at low cost and on a large scale. The photoresist composition containing the photosensitive agent exhibits satisfactory sensitivity suitable for producing semiconductor integrated circuits, liquid crystal displays, EL displays, etc. through ultra-fine photolithography, as well as excellent storage stability, finding remarkable utility in practice. In particular, the photoresist composition is usefully employed for exposure to i-line.